I can give you a computer speed that I have tried and does not work..
VIA C7 1.5GHz
It's a popular chipset and I am sure many have wondered about this.. so there is the answer.
The soundcard that I did get to work is the
Presonus Firebox. http://www.presonus.com/firebox.html
This was with fully active VAC, and the free versions of Console and ASIO4All.
I used a multimeter to measure the Signal voltage of the firebox. I got between 5-7 volts before clipping. If I recall correctly, Up to 10 -13 volts clipping. It has six ouputs, one headphone out, 4 inputs and can be powered through firewire. Pretty decent card for software ASIO based tuning.